Securing encoding data slices using an integrity check value list

ABSTRACT

A method includes retrieving a read threshold number of integrity check value list (ICVL) encoded data slices of a set of ICVL encoded data slices. The method further includes determining whether an appended ICVL of each ICVL encoded data slice of the read threshold number of ICVL encoded data slices substantially match. When the appended ICVL of one of the ICVL encoded does not substantially match the appended ICVL of other ICVL encoded data slices, the method further includes determining a likely cause for the mismatch. When the likely cause is missing a revision update, the method further includes initiate rebuilding of the encoded data slice portion. The method further includes generating an integrity check value for the rebuilt encoded data slice and updating the integrity check value list. The method further includes appending the updated integrity check value list to the rebuilt encoded data slice.

CROSS REFERENCE TO RELATED PATENTS

The present U.S. Utility Patent Application also claims prioritypursuant to 35 U.S.C. § 120, as a continuation of U.S. Utility patentapplication Ser. No. 15/357,293, entitled “SECURING ENCODING DATA SLICESUSING AN INTEGRITY CHECK VALUE LIST,” filed Nov. 21, 2016, pending,which claims priority pursuant to 35 U.S.C. § 119(e) to U.S. ProvisionalApplication No. 62/260,743, entitled “COMMUNICATING DISPERSED STORAGENETWORK STORAGE UNIT TASK EXECUTION STATUS”, filed Nov. 30, 2015, bothof which are hereby incorporated herein by reference in their entiretyand made part of the present U.S. Utility Patent Application for allpurposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable.

BACKGROUND OF THE INVENTION Technical Field of the Invention

This invention relates generally to computer networks and moreparticularly to dispersing error encoded data.

Description of Related Art

Computing devices are known to communicate data, process data, and/orstore data. Such computing devices range from wireless smart phones,laptops, tablets, personal computers (PC), work stations, and video gamedevices, to data centers that support millions of web searches, stocktrades, or on-line purchases every day. In general, a computing deviceincludes a central processing unit (CPU), a memory system, userinput/output interfaces, peripheral device interfaces, and aninterconnecting bus structure.

As is further known, a computer may effectively extend its CPU by using“cloud computing” to perform one or more computing functions (e.g., aservice, an application, an algorithm, an arithmetic logic function,etc.) on behalf of the computer. Further, for large services,applications, and/or functions, cloud computing may be performed bymultiple cloud computing resources in a distributed manner to improvethe response time for completion of the service, application, and/orfunction. For example, Hadoop is an open source software framework thatsupports distributed applications enabling application execution bythousands of computers.

In addition to cloud computing, a computer may use “cloud storage” aspart of its memory system. As is known, cloud storage enables a user,via its computer, to store files, applications, etc. on an Internetstorage system. The Internet storage system may include a RAID(redundant array of independent disks) system and/or a dispersed storagesystem that uses an error correction scheme to encode data for storage.

For cloud storage systems, security is an on-going challenge. Breachprevention major and breach detection are two primary issues for securecloud storage operation. Breach prevention is directed towardspreventing unauthorized access to the cloud storage system. Breachdetection is directed towards detecting a potential unauthorized access,determining with it is unauthorized, and, if it is, taking correctivemeasures. Such corrective measures includes updating breach detection,removing hardware from the system, attempting to recover compromiseddata, etc.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a dispersed ordistributed storage network (DSN) in accordance with the presentinvention;

FIG. 2 is a schematic block diagram of an embodiment of a computing corein accordance with the present invention;

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data in accordance with the present invention;

FIG. 4 is a schematic block diagram of a generic example of an errorencoding function in accordance with the present invention;

FIG. 5 is a schematic block diagram of a specific example of an errorencoding function in accordance with the present invention;

FIG. 6 is a schematic block diagram of an example of a slice name of anencoded data slice (EDS) in accordance with the present invention;

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of data in accordance with the present invention;

FIG. 8 is a schematic block diagram of a generic example of an errordecoding function in accordance with the present invention;

FIG. 9A is a schematic block diagram of an example of a plurality ofsets of encoded data slices (EDS) in accordance with the presentinvention;

FIG. 9B is a schematic block diagram of an example of a plurality ofsets of integrity check value list (ICVL) encoded data slices (EDS) inaccordance with the present invention;

FIG. 10A is a schematic block diagram of another example of a pluralityof sets of encoded data slices (EDS) in accordance with the presentinvention;

FIG. 10B is a schematic block diagram of another example of a pluralityof sets of integrity check value list (ICVL) encoded data slices (EDS)in accordance with the present invention;

FIG. 11 is a schematic block diagram of an example of a set of integritycheck value list (ICVL) encoded data slices (EDS) having substantiallymatching ICVLs in accordance with the present invention;

FIG. 12 is a schematic block diagram of an example of a set of integritycheck value list (ICVL) encoded data slices (EDS) having a mismatchingICVL in accordance with the present invention;

FIG. 13 is a schematic block diagram of another example of a set ofintegrity check value list (ICVL) encoded data slices (EDS) having amismatching ICVL in accordance with the present invention;

FIG. 14 is a schematic block diagram of another example of a set ofintegrity check value list (ICVL) encoded data slices (EDS) having amismatching ICVL in accordance with the present invention;

FIG. 15 is a logic diagram of an example of a method of creating one ormore sets of integrity check value list (ICVL) encoded data slices (EDS)in accordance with the present invention; and

FIG. 16 is a logic diagram of an example of a method of accessing one ormore sets of integrity check value list (ICVL) encoded data slices (EDS)in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a dispersed, ordistributed, storage network (DSN) 10 that includes a plurality ofcomputing devices 12-16, a managing unit 18, an integrity processingunit 20, and a DSN memory 22. The components of the DSN 10 are coupledto a network 24, which may include one or more wireless and/or wirelined communication systems; one or more non-public intranet systemsand/or public internet systems; and/or one or more local area networks(LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of storage units 36 that may belocated at geographically different sites (e.g., one in Chicago, one inMilwaukee, etc.), at a common site, or a combination thereof. Forexample, if the DSN memory 22 includes eight storage units 36, eachstorage unit is located at a different site. As another example, if theDSN memory 22 includes eight storage units 36, all eight storage unitsare located at the same site. As yet another example, if the DSN memory22 includes eight storage units 36, a first pair of storage units are ata first common site, a second pair of storage units are at a secondcommon site, a third pair of storage units are at a third common site,and a fourth pair of storage units are at a fourth common site. Notethat a DSN memory 22 may include more or less than eight storage units36. Further note that each storage unit 36 includes a computing core (asshown in FIG. 2, or components thereof) and a plurality of memorydevices for storing dispersed error encoded data.

Each of the computing devices 12-16, the managing unit 18, and theintegrity processing unit 20 include a computing core 26, which includesnetwork interfaces 30-33. Computing devices 12-16 may each be a portablecomputing device and/or a fixed computing device. A portable computingdevice may be a social networking device, a gaming device, a cell phone,a smart phone, a digital assistant, a digital music player, a digitalvideo player, a laptop computer, a handheld computer, a tablet, a videogame controller, and/or any other portable device that includes acomputing core. A fixed computing device may be a computer (PC), acomputer server, a cable set-top box, a satellite receiver, a televisionset, a printer, a fax machine, home entertainment equipment, a videogame console, and/or any type of home or office computing equipment.Note that each of the managing unit 18 and the integrity processing unit20 may be separate computing devices, may be a common computing device,and/or may be integrated into one or more of the computing devices 12-16and/or into one or more of the storage units 36.

Each interface 30, 32, and 33 includes software and hardware to supportone or more communication links via the network 24 indirectly and/ordirectly. For example, interface 30 supports a communication link (e.g.,wired, wireless, direct, via a LAN, via the network 24, etc.) betweencomputing devices 14 and 16. As another example, interface 32 supportscommunication links (e.g., a wired connection, a wireless connection, aLAN connection, and/or any other type of connection to/from the network24) between computing devices 12 and 16 and the DSN memory 22. As yetanother example, interface 33 supports a communication link for each ofthe managing unit 18 and the integrity processing unit 20 to the network24.

Computing devices 12 and 16 include a dispersed storage (DS) clientmodule 34, which enables the computing device to dispersed storage errorencode and decode data (e.g., data 40) as subsequently described withreference to one or more of FIGS. 3-8. In this example embodiment,computing device 16 functions as a dispersed storage processing agentfor computing device 14. In this role, computing device 16 dispersedstorage error encodes and decodes data on behalf of computing device 14.With the use of dispersed storage error encoding and decoding, the DSN10 is tolerant of a significant number of storage unit failures (thenumber of failures is based on parameters of the dispersed storage errorencoding function) without loss of data and without the need for aredundant or backup copies of the data. Further, the DSN 10 stores datafor an indefinite period of time without data loss and in a securemanner (e.g., the system is very resistant to unauthorized attempts ataccessing the data).

In operation, the managing unit 18 performs DS management services. Forexample, the managing unit 18 establishes distributed data storageparameters (e.g., vault creation, distributed storage parameters,security parameters, billing information, user profile information,etc.) for computing devices 12-14 individually or as part of a group ofuser devices. As a specific example, the managing unit 18 coordinatescreation of a vault (e.g., a virtual memory block associated with aportion of an overall namespace of the DSN) within the DSN memory 22 fora user device, a group of devices, or for public access and establishesper vault dispersed storage (DS) error encoding parameters for a vault.The managing unit 18 facilitates storage of DS error encoding parametersfor each vault by updating registry information of the DSN 10, where theregistry information may be stored in the DSN memory 22, a computingdevice 12-16, the managing unit 18, and/or the integrity processing unit20.

The managing unit 18 creates and stores user profile information (e.g.,an access control list (ACL)) in local memory and/or within memory ofthe DSN memory 22. The user profile information includes authenticationinformation, permissions, and/or the security parameters. The securityparameters may include encryption/decryption scheme, one or moreencryption keys, key generation scheme, and/or data encoding/decodingscheme.

The managing unit 18 creates billing information for a particular user,a user group, a vault access, public vault access, etc. For instance,the managing unit 18 tracks the number of times a user accesses anon-public vault and/or public vaults, which can be used to generate aper-access billing information. In another instance, the managing unit18 tracks the amount of data stored and/or retrieved by a user deviceand/or a user group, which can be used to generate a per-data-amountbilling information.

As another example, the managing unit 18 performs network operations,network administration, and/or network maintenance. Network operationsincludes authenticating user data allocation requests (e.g., read and/orwrite requests), managing creation of vaults, establishingauthentication credentials for user devices, adding/deleting components(e.g., user devices, storage units, and/or computing devices with a DSclient module 34) to/from the DSN 10, and/or establishing authenticationcredentials for the storage units 36. Network administration includesmonitoring devices and/or units for failures, maintaining vaultinformation, determining device and/or unit activation status,determining device and/or unit loading, and/or determining any othersystem level operation that affects the performance level of the DSN 10.Network maintenance includes facilitating replacing, upgrading,repairing, and/or expanding a device and/or unit of the DSN 10.

The integrity processing unit 20 performs rebuilding of ‘bad’ or missingencoded data slices. At a high level, the integrity processing unit 20performs rebuilding by periodically attempting to retrieve/list encodeddata slices, and/or slice names of the encoded data slices, from the DSNmemory 22. For retrieved encoded slices, they are checked for errors dueto data corruption, outdated version, etc. If a slice includes an error,it is flagged as a ‘bad’ slice. For encoded data slices that were notreceived and/or not listed, they are flagged as missing slices. Badand/or missing slices are subsequently rebuilt using other retrievedencoded data slices that are deemed to be good slices to produce rebuiltslices. The rebuilt slices are stored in the DSN memory 22.

FIG. 2 is a schematic block diagram of an embodiment of a computing core26 that includes a processing module 50, a memory controller 52, mainmemory 54, a video graphics processing unit 55, an input/output (TO)controller 56, a peripheral component interconnect (PCI) interface 58,an IO interface module 60, at least one IO device interface module 62, aread only memory (ROM) basic input output system (BIOS) 64, and one ormore memory interface modules. The one or more memory interfacemodule(s) includes one or more of a universal serial bus (USB) interfacemodule 66, a host bus adapter (HBA) interface module 68, a networkinterface module 70, a flash interface module 72, a hard drive interfacemodule 74, and a DSN interface module 76.

The DSN interface module 76 functions to mimic a conventional operatingsystem (OS) file system interface (e.g., network file system (NFS),flash file system (FFS), disk file system (DFS), file transfer protocol(FTP), web-based distributed authoring and versioning (WebDAV), etc.)and/or a block memory interface (e.g., small computer system interface(SCSI), internet small computer system interface (iSCSI), etc.). The DSNinterface module 76 and/or the network interface module 70 may functionas one or more of the interface 30-33 of FIG. 1. Note that the IO deviceinterface module 62 and/or the memory interface modules 66-76 may becollectively or individually referred to as IO ports.

FIG. 3 is a schematic block diagram of an example of dispersed storageerror encoding of data. When a computing device 12 or 16 has data tostore it disperse storage error encodes the data in accordance with adispersed storage error encoding process based on dispersed storageerror encoding parameters. The dispersed storage error encodingparameters include an encoding function (e.g., information dispersalalgorithm, Reed-Solomon, Cauchy Reed-Solomon, systematic encoding,non-systematic encoding, on-line codes, etc.), a data segmentingprotocol (e.g., data segment size, fixed, variable, etc.), and per datasegment encoding values. The per data segment encoding values include atotal, or pillar width, number (T) of encoded data slices per encodingof a data segment (i.e., in a set of encoded data slices); a decodethreshold number (D) of encoded data slices of a set of encoded dataslices that are needed to recover the data segment; a read thresholdnumber (R) of encoded data slices to indicate a number of encoded dataslices per set to be read from storage for decoding of the data segment;and/or a write threshold number (W) to indicate a number of encoded dataslices per set that must be accurately stored before the encoded datasegment is deemed to have been properly stored. The dispersed storageerror encoding parameters may further include slicing information (e.g.,the number of encoded data slices that will be created for each datasegment) and/or slice security information (e.g., per encoded data sliceencryption, compression, integrity checksum, etc.).

In the present example, Cauchy Reed-Solomon has been selected as theencoding function (a generic example is shown in FIG. 4 and a specificexample is shown in FIG. 5); the data segmenting protocol is to dividethe data object into fixed sized data segments; and the per data segmentencoding values include: a pillar width of 5, a decode threshold of 3, aread threshold of 4, and a write threshold of 4. In accordance with thedata segmenting protocol, the computing device 12 or 16 divides the data(e.g., a file (e.g., text, video, audio, etc.), a data object, or otherdata arrangement) into a plurality of fixed sized data segments (e.g., 1through Y of a fixed size in range of Kilo-bytes to Tera-bytes or more).The number of data segments created is dependent of the size of the dataand the data segmenting protocol.

The computing device 12 or 16 then disperse storage error encodes a datasegment using the selected encoding function (e.g., Cauchy Reed-Solomon)to produce a set of encoded data slices. FIG. 4 illustrates a genericCauchy Reed-Solomon encoding function, which includes an encoding matrix(EM), a data matrix (DM), and a coded matrix (CM). The size of theencoding matrix (EM) is dependent on the pillar width number (T) and thedecode threshold number (D) of selected per data segment encodingvalues. To produce the data matrix (DM), the data segment is dividedinto a plurality of data blocks and the data blocks are arranged into Dnumber of rows with Z data blocks per row. Note that Z is a function ofthe number of data blocks created from the data segment and the decodethreshold number (D). The coded matrix is produced by matrix multiplyingthe data matrix by the encoding matrix.

FIG. 5 illustrates a specific example of Cauchy Reed-Solomon encodingwith a pillar number (T) of five and decode threshold number of three.In this example, a first data segment is divided into twelve data blocks(D1-D12). The coded matrix includes five rows of coded data blocks,where the first row of X11-X14 corresponds to a first encoded data slice(EDS 1_1), the second row of X21-X24 corresponds to a second encodeddata slice (EDS 2_1), the third row of X31-X34 corresponds to a thirdencoded data slice (EDS 3_1), the fourth row of X41-X44 corresponds to afourth encoded data slice (EDS 4_1), and the fifth row of X51-X54corresponds to a fifth encoded data slice (EDS 5_1). Note that thesecond number of the EDS designation corresponds to the data segmentnumber.

Returning to the discussion of FIG. 3, the computing device also createsa slice name (SN) for each encoded data slice (EDS) in the set ofencoded data slices. A typical format for a slice name 80 is shown inFIG. 6. As shown, the slice name (SN) 80 includes a pillar number of theencoded data slice (e.g., one of 1-T), a data segment number (e.g., oneof 1-Y), a vault identifier (ID), a data object identifier (ID), and mayfurther include revision level information of the encoded data slices.The slice name functions as, at least part of, a DSN address for theencoded data slice for storage and retrieval from the DSN memory 22.

As a result of encoding, the computing device 12 or 16 produces aplurality of sets of encoded data slices, which are provided with theirrespective slice names to the storage units for storage. As shown, thefirst set of encoded data slices includes EDS 1_1 through EDS 5_1 andthe first set of slice names includes SN 1_1 through SN 5_1 and the lastset of encoded data slices includes EDS 1_Y through EDS 5_Y and the lastset of slice names includes SN 1_Y through SN 5_Y.

FIG. 7 is a schematic block diagram of an example of dispersed storageerror decoding of a data object that was dispersed storage error encodedand stored in the example of FIG. 4. In this example, the computingdevice 12 or 16 retrieves from the storage units at least the decodethreshold number of encoded data slices per data segment. As a specificexample, the computing device retrieves a read threshold number ofencoded data slices.

To recover a data segment from a decode threshold number of encoded dataslices, the computing device uses a decoding function as shown in FIG.8. As shown, the decoding function is essentially an inverse of theencoding function of FIG. 4. The coded matrix includes a decodethreshold number of rows (e.g., three in this example) and the decodingmatrix in an inversion of the encoding matrix that includes thecorresponding rows of the coded matrix. For example, if the coded matrixincludes rows 1, 2, and 4, the encoding matrix is reduced to rows 1, 2,and 4, and then inverted to produce the decoding matrix.

FIG. 9A is a schematic block diagram of an example of a plurality ofsets of encoded data slices (EDS). As previously discussed, a computingdevice divides a data object into a plurality of data segments. It thendispersed storage error encodes each data segment to produce a set ofencoded data slices and a corresponding set of slice names (SN). In thisexample, the computing device further generates an integrity check value(ICV) for each encoded data slice (EDS). The ICV may be created in avariety of ways. For example, the ICV is generated using a hashfunction. As another example, the ICV is generated used a cyclicredundancy check (CRC) function.

An integrity check value list (ICVL) is created from the integrity checkvalues (ICVs) of each encoded data slice (EDS) of a set of encoded dataslices. For example, a first data segment is dispersed storage errorencoded into a set of EDSs having a set of slice names (SN). Inparticular, five EDSs and SNs are created for this set: 1_1_1_1_a 1;2_1_1_1_a 1; 3_1_1_1_a 1; 4_1_1_1_a 1; and 5_1_1_1_a 1. The first digitof the EDS and SN represents the slice number in the set (e.g., 1-5);The second digit represents the segment number (e.g., 1-Y); the thirddigit represents the vault number (e.g., a logical storage container ofthe DSN having one or more user devices affiliated with it); The fourthdigit represents the current revision number of the EDS; The fifth value(e.g., a1) represents a data object identifier.

Continuing with the example, for each encoded data slice (EDS) and/orslice name (SN) of the set, an integrity check value is created. As aspecific example, an ICV is generated from the encoded data slice, theslice name, or both the encoded data slice and the slice name. Forinstance, ICV 1_1_1_1_a 1 is created for EDS 1_1_1_1_a 1 and/or SN1_1_1_1_a 1. The ICVs for the set (e.g., ICV 1_1_1_1_a 1 through ICV5_1_1_1_a 1) are combined (e.g., added to the list “as is”,mathematically manipulated, etc.) to produce the integrity check valuelist (IVCL) 1_1_1_a 1 (e.g., ICVL regarding the first segment, vault 1,revision number 1 of data object a1). For each set of EDSs, acorresponding ICVL is created.

FIG. 9B is a schematic block diagram of an example of a plurality ofsets of integrity check value list (ICVL) encoded data slices (EDS).Prior to sending the plurality of sets of EDSs to a set of storage unitsfor storage, the computing device appends an ICVL to each EDS to createthe plurality of sets of ICVL EDSs. For example, for the first set ofencoded data slices (e.g., EDS 1_1_1_1_a 1 through EDS 5_1_1_1_a 1) thecomputing device appends ICVL 1_1_1_a 1 to each EDS. As another example,for the Yth set of encoded data slices (e.g., EDS 1_Y_1_1_a 1 throughEDS 5_Y_1_1_a 1) the computing device appends ICVL Y_1_1_a 1 to eachEDS. Once the IVCLs are appended, the computing device sends the set ofICVL EDSs to the set of storage units (e.g., SU #1-SU #5).

Within a storage unit, the ICVL may be affiliated with the slice nameand/or the encoded data slice. For example, for a read request, thestorage unit affiliates the ICVL with the EDS and SN to produce ICVLencoded data slice 75 and sends the ICVL EDS 75 to the requestingcomputing device. In another example, such as for a list or rebuildcheck request, the storage unit affiliates the ICVL with the slice nameto produce ICVL encoded data slice 77 and sends ICVL EDS 77 to therequesting device (e.g., computing device or another storage unit).

FIG. 10A is a schematic block diagram of another example of a pluralityof sets of encoded data slices (EDS). This example is similar to the oneof FIG. 9A, but the integrity check value (ICV) of each EDS of theplurality of sets of EDSs are combined to produce one integrity checkvalue list (ICVL). For instance, ICV 1_1_1_1_a 1 through ICV 5_Y_1_1_a 1are combined to produce ICVL 1_1_a 1 (e.g., the integrity check valuelist for vault 1, revision number 1 of data object a1). Note thatintegrity check value lists may be created for any combination of setsof encoded data slices for one or more data objects. For example, twosets of ICVs (e.g., for two sets of EDSs and/or SNs) are used to producea single ICVL that is appended to each EDS and/or SN of the two sets.

FIG. 10B is a schematic block diagram of another example of a pluralityof sets of integrity check value list (ICVL) encoded data slices (EDS).This is example is similar to the one of FIG. 9B, but each EDS in theplurality of sets of EDSs has appended thereto the same ICVL (e.g.,1_1_a 1).

Within a storage unit, the ICVL (e.g., 1_1_a 1) may be affiliated withthe slice name and/or the encoded data slice. For example, for a readrequest, the storage unit affiliates the ICVL with the EDS and SN toproduce ICVL encoded data slice 81 and sends the ICVL EDS 81 to therequesting computing device. In another example, such as for a list orrebuild check request, the storage unit affiliates the ICVL with theslice name to produce ICVL encoded data slice 83 and sends ICVL EDS 83to the requesting device (e.g., computing device or another storageunit).

FIG. 11 is a schematic block diagram of an example of a set of integritycheck value list (ICVL) encoded data slices (EDS) having substantiallymatching ICVLs. In this example, a requesting computing device issued aread request to the storage units for set 1 of the plurality of sets ofencoded data slices of data object “a1”. Each of the responding storageunits (e.g., a decode threshold, a read threshold, all, etc.) respond byproviding the slice name, the encoded data slice, and the integritycheck value list (ICVL).

In this example, each slice has the same list (e.g., ICVL 1_1_a 1)indicating to the requesting device that the slices are current andaccurate (e.g., have not been corrupted due to failing hardware,hardware being offline, and/or unauthorized modifications, deletions,etc.). Note that, for a list or rebuild check request, the storage unitswould respond with the slice name and the ICVL, omitting the EDS.

FIG. 12 is a schematic block diagram of an example of a set of integritycheck value list (ICVL) encoded data slices (EDS) having a mismatchingICVL. In this example, a requesting computing device issued a readrequest to the storage units for revision 2 of set 1 of the plurality ofsets of encoded data slices of data object “a1”. Each of the respondingstorage units (e.g., a decode threshold, a read threshold, all, etc.)respond by providing the slice name, the encoded data slice, and theintegrity check value list (ICVL).

In this example, slice #3 has a different list (e.g., ICVL 1_1_a 1) thanthe list of the other slices (e.g., ICVL 1_2_a 1). When a mismatch inthe lists is detected, the computing device determines a likely causefor the mismatch. A likely cause includes, but is not limited to, astorage unit having failing memory, a storage unit being off line duringa revision update, an error in transmission, and/or unauthorizedmodifications, deletions, etc. In this example, the mismatch is likelydue to the storage unit being offline during a revision update since therevision number of EDS #3 is not the same as the revision number of theother EDSs. As such, the computing device would initiate a rebuildfunction for encoded data slice #3 of set 1 of data object a1.

FIG. 13 is a schematic block diagram of another example of a set ofintegrity check value list (ICVL) encoded data slices (EDS) having amismatching ICVL. In this example, a requesting computing device issueda read request to the storage units for revision 1 of set 1 of theplurality of sets of encoded data slices of data object “a1”. Each ofthe responding storage units (e.g., a decode threshold, a readthreshold, all, etc.) respond by providing the slice name, the encodeddata slice, and the integrity check value list (ICVL).

In this example, slice #4 has a different list (e.g., ICVL 1′_1′_a 1′)than the list of the other slices (e.g., ICVL 1_1_a 1). When a mismatchin the lists is detected, the computing device determines a likely causefor the mismatch. In this example, the computing device computes anintegrity check value (ICV) of EDS 4_1_1_1_a 1 and/or of SN 4_1_1_1_a 1.If the newly computed ICV matches the ICV in the ICL list, then thelikely cause for the mismatch is the storage unit having failing memoryand/or an error in transmission. When this is the case, the requestingcomputing device can use EDS #4 in recovering the corresponding datasegment with confidence that it is current and accurate.

FIG. 14 is a schematic block diagram of another example of a set ofintegrity check value list (ICVL) encoded data slices (EDS) having amismatching ICVL. In this example, a requesting computing device issueda read request to the storage units for revision 1 of set 1 of theplurality of sets of encoded data slices of data object “a1”. Each ofthe responding storage units (e.g., a decode threshold, a readthreshold, all, etc.) respond by providing the slice name, the encodeddata slice, and the integrity check value list (ICVL).

In this example, slice #3 has a different list (e.g., ICV 3_1_1_a 1)than the list of the other slices (e.g., ICVL 1_1_a 1). In particular,the ICV list of slice #3 is not a list, but the integrity check value.With this type of mismatch, the computing device determines the likelycause to be an unauthorized modification of slice #3. In this instance,the computing device initiates a corrective measure, which includesrebuilding the EDS when deemed to be a non-harmful unauthorizedmodification; decommissioning the storage unit; quarantining the storageunit (e.g., restrict and control communication with the storage unit),and/or a higher level of security regarding access to the storage unit.

FIG. 15 is a logic diagram of an example of a method of creating one ormore sets of integrity check value list (ICVL) encoded data slices(EDS). The method begins at step 90 where a computing device dispersedstorage error encodes a data segment of a data object into a set ofencoded data slices (EDSs). The method continues at step 92 where thecomputing device generates a set of integrity check values (ICVs) for aset of encoded data slices. Examples of generating the ICVs werepreviously discussed.

The method continues at step 94 where the computing device generates anintegrity check value list (ICVL) from the set of integrity checkvalues. FIGS. 9A and 10A provide examples of generating the list. Themethod continues at step 96 where the computing device appends theintegrity check value list (ICVL) to each encoded data slice of the setof encoded data slices to produce a set of ICVL encoded data slices.FIGS. 9B and 10B provide examples of appending the list. The methodcontinues at step 98 where the computing device sends the set of ICVLencoded data slices to the set of storage units of the DSN for storagetherein.

FIG. 16 is a logic diagram of an example of a method of accessing one ormore sets of integrity check value list (ICVL) encoded data slices(EDS). The method begins at step 100 where the computing device (e.g.,the one that created the set of ICVL EDSs) and/or another computingdevice (e.g., authorized to access the set of ICVL EDSs) retrieve a readthreshold number of integrity check value list (ICVL) encoded dataslices of a set of ICVL encoded data slices from at least some of thestorage units. Note that the read threshold is a number of desiredresponses to a read request in a range between the decode threshold andthe pillar width number. For example, the computing device and/or theother computing devices issues a read request, a list request, or arebuild check request to the storage units. The storage units respondbased on the type of request as discussed with reference to FIGS. 9B and10B.

The method continues at step 102 where the computing device and/or theother one, determines whether the appended ICVL of each ICVL encodeddata slice substantially match. If yes, the method continues at step104, where the computing device and/or the other one processes therequest (e.g., read, list, rebuild check, etc.)

When one more of the appended ICVL of one of the ICVL encoded dataslices does not substantially match the others, the method continues atstep 106 where the computing device and/or the other one determines alikely cause for the mismatch. The method continues at step 108 wherethe computing device and/or the other one determines whether the likelycause is a missed revision update (e.g., as discussed with reference toFIG. 12).

If yes, the method continues at step 110 where the computing deviceand/or the other one initiates rebuilding of the encoded data slice. Themethod continues at step 112 where the computing device and/or the otherone generates an integrity check value for the rebuilt encoded dataslice. The method continues at step 114 where the computing deviceand/or the other one generates an updated integrity check value listincluding the integrity check value for the rebuilt encoded data sliceand integrity check values of the encoded data slices of the other ICVLencoded data slices.

The method continues at step 116 where the computing device and/or theother one appends the updated integrity check value list to the rebuiltencoded data slice to produce a rebuild ICVL encoded data slice. Themethod continues at step 118 where the computing device and/or the otherone sends the rebuilt ICVL encoded data slice one of the storage unitsfor storage therein.

When the likely cause for the mismatch is not a missed revision update,the method continues at step 120 where the computing device and/or theother one determines whether the likely cause is an inaccurate integritycheck value list (ICVL) appended to the one of the ICVL encoded dataslices (e.g., as discussed with reference to FIG. 13). If yes, themethod continues at step 124 where the computing device and/or the otherone calculates a new integrity check value for an encoded data sliceportion of the one of the ICVL encoded data slices. The method continuesat step 126 where the computing device and/or the other one extracts theintegrity check value for the slice from the appended ICVL of anotherslice.

The method continues at step 128 where the computing device and/or theother one determines whether the new integrity check value substantiallymatches the extracted integrity check value. If yes, the methodcontinues at step 130 where the computing device and/or the other oneuses the encoded data slice in recovering the data segment. If not, themethod continues at step 110.

When the likely cause is not an inaccurate integrity check value list(ICVL) appended to the slice, the method continues at step 122 where thecomputing device and/or the other one takes corrective measures for anunauthorized modification. For example, the computing device and/or theother one sends a delete message to a storage unit storing the one ofthe ICVL encoded data slices. As another example, the computing deviceand/or the other one initiates a rebuild process as discussed in steps110-118. As yet another example, the computing device and/or the otherone initiates a decommissioning of the storage unit, a quarantine of thestorage unit, and a higher level of security regarding access to thestorage unit.

It is noted that terminologies as may be used herein such as bit stream,stream, signal sequence, etc. (or their equivalents) have been usedinterchangeably to describe digital information whose contentcorresponds to any of a number of desired types (e.g., data, video,speech, audio, etc. any of which may generally be referred to as‘data’).

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “configured to”, “operably coupled to”, “coupled to”, and/or“coupling” includes direct coupling between items and/or indirectcoupling between items via an intervening item (e.g., an item includes,but is not limited to, a component, an element, a circuit, and/or amodule) where, for an example of indirect coupling, the intervening itemdoes not modify the information of a signal but may adjust its currentlevel, voltage level, and/or power level. As may further be used herein,inferred coupling (i.e., where one element is coupled to another elementby inference) includes direct and indirect coupling between two items inthe same manner as “coupled to”. As may even further be used herein, theterm “configured to”, “operable to”, “coupled to”, or “operably coupledto” indicates that an item includes one or more of power connections,input(s), output(s), etc., to perform, when activated, one or more itscorresponding functions and may further include inferred coupling to oneor more other items. As may still further be used herein, the term“associated with”, includes direct and/or indirect coupling of separateitems and/or one item being embedded within another item.

As may be used herein, the term “compares favorably”, indicates that acomparison between two or more items, signals, etc., provides a desiredrelationship. For example, when the desired relationship is that signal1 has a greater magnitude than signal 2, a favorable comparison may beachieved when the magnitude of signal 1 is greater than that of signal 2or when the magnitude of signal 2 is less than that of signal 1. As maybe used herein, the term “compares unfavorably”, indicates that acomparison between two or more items, signals, etc., fails to providethe desired relationship.

As may also be used herein, the terms “processing module”, “processingcircuit”, “processor”, and/or “processing unit” may be a singleprocessing device or a plurality of processing devices. Such aprocessing device may be a microprocessor, micro-controller, digitalsignal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on hard coding of thecircuitry and/or operational instructions. The processing module,module, processing circuit, and/or processing unit may be, or furtherinclude, memory and/or an integrated memory element, which may be asingle memory device, a plurality of memory devices, and/or embeddedcircuitry of another processing module, module, processing circuit,and/or processing unit. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, cache memory, and/or any devicethat stores digital information. Note that if the processing module,module, processing circuit, and/or processing unit includes more thanone processing device, the processing devices may be centrally located(e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that if the processing module, module, processing circuit,and/or processing unit implements one or more of its functions via astate machine, analog circuitry, digital circuitry, and/or logiccircuitry, the memory and/or memory element storing the correspondingoperational instructions may be embedded within, or external to, thecircuitry comprising the state machine, analog circuitry, digitalcircuitry, and/or logic circuitry. Still further note that, the memoryelement may store, and the processing module, module, processingcircuit, and/or processing unit executes, hard coded and/or operationalinstructions corresponding to at least some of the steps and/orfunctions illustrated in one or more of the Figures. Such a memorydevice or memory element can be included in an article of manufacture.

One or more embodiments have been described above with the aid of methodsteps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claims. Further, the boundariesof these functional building blocks have been arbitrarily defined forconvenience of description. Alternate boundaries could be defined aslong as the certain significant functions are appropriately performed.Similarly, flow diagram blocks may also have been arbitrarily definedherein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence couldhave been defined otherwise and still perform the certain significantfunctionality. Such alternate definitions of both functional buildingblocks and flow diagram blocks and sequences are thus within the scopeand spirit of the claims. One of average skill in the art will alsorecognize that the functional building blocks, and other illustrativeblocks, modules and components herein, can be implemented as illustratedor by discrete components, application specific integrated circuits,processors executing appropriate software and the like or anycombination thereof.

In addition, a flow diagram may include a “start” and/or “continue”indication. The “start” and “continue” indications reflect that thesteps presented can optionally be incorporated in or otherwise used inconjunction with other routines. In this context, “start” indicates thebeginning of the first step presented and may be preceded by otheractivities not specifically shown. Further, the “continue” indicationreflects that the steps presented may be performed multiple times and/ormay be succeeded by other activities not specifically shown. Further,while a flow diagram indicates a particular ordering of steps, otherorderings are likewise possible provided that the principles ofcausality are maintained.

The one or more embodiments are used herein to illustrate one or moreaspects, one or more features, one or more concepts, and/or one or moreexamples. A physical embodiment of an apparatus, an article ofmanufacture, a machine, and/or of a process may include one or more ofthe aspects, features, concepts, examples, etc. described with referenceto one or more of the embodiments discussed herein. Further, from figureto figure, the embodiments may incorporate the same or similarly namedfunctions, steps, modules, etc. that may use the same or differentreference numbers and, as such, the functions, steps, modules, etc. maybe the same or similar functions, steps, modules, etc. or differentones.

Unless specifically stated to the contra, signals to, from, and/orbetween elements in a figure of any of the figures presented herein maybe analog or digital, continuous time or discrete time, and single-endedor differential. For instance, if a signal path is shown as asingle-ended path, it also represents a differential signal path.Similarly, if a signal path is shown as a differential path, it alsorepresents a single-ended signal path. While one or more particulararchitectures are described herein, other architectures can likewise beimplemented that use one or more data buses not expressly shown, directconnectivity between elements, and/or indirect coupling between otherelements as recognized by one of average skill in the art.

The term “module” is used in the description of one or more of theembodiments. A module implements one or more functions via a device suchas a processor or other processing device or other hardware that mayinclude or operate in association with a memory that stores operationalinstructions. A module may operate independently and/or in conjunctionwith software and/or firmware. As also used herein, a module may containone or more sub-modules, each of which may be one or more modules.

As may further be used herein, a computer readable memory includes oneor more memory elements. A memory element may be a separate memorydevice, multiple memory devices, or a set of memory locations within amemory device. Such a memory device may be a read-only memory, randomaccess memory, volatile memory, non-volatile memory, static memory,dynamic memory, flash memory, cache memory, and/or any device thatstores digital information. The memory device may be in a form a solidstate memory, a hard drive memory, cloud memory, thumb drive, servermemory, computing device memory, and/or other physical medium forstoring digital information.

While particular combinations of various functions and features of theone or more embodiments have been expressly described herein, othercombinations of these features and functions are likewise possible. Thepresent disclosure is not limited by the particular examples disclosedherein and expressly incorporates these other combinations.

What is claimed is:
 1. A computing device comprising: an interfaceconfigured to interface and communicate with a dispersed storage network(DSN); memory that stores operational instructions; and processingcircuitry operably coupled to the interface and to the memory, whereinthe processing circuitry is configured to execute the operationalinstructions to: retrieve a read threshold number of integrity checkvalue list (ICVL) encoded data slices (EDSs) of a set of ICVL EDSs fromat least some storage units (SUs) of a set of SUs based on a request;determine whether an appended ICVL of each ICVL EDS of the readthreshold number of ICVL EDSs substantially match; based ondetermination that the appended ICVL of one of the ICVL EDSs of the readthreshold number of ICVL EDSs does not substantially match the appendedICVL of other ICVL EDSs of the read threshold number of ICVL EDSs:determine a likely cause for the appended ICVL of the one of the ICVLEDSs not substantially matching the appended ICVL of the other ICVLEDSs; and based on determination that the likely cause is an inaccurateICVL appended to the one of the ICVL EDSs: calculate a new integritycheck value for an EDS portion of the one of the ICVL EDSs; extract anintegrity check value from the appended ICVL of one of the other ICVLEDSs to produce an extracted integrity check value; compare the newintegrity check value with the extracted integrity check value; andbased on determination that the new integrity check value substantiallymatches the extracted integrity check value, utilize the EDS in decodingof the read threshold number of EDSs to recover a data segment of a dataobject.
 2. The computing device of claim 1, wherein the processingcircuitry is further configured to execute the operational instructionsto: based on determination that the likely cause is not the inaccurateICVL appended to the one of the ICVL EDSs and also is not missing arevision update, take at least one corrective measure for anunauthorized modification that includes at least one of sending a deletemessage to a SU storing the one of the ICVL EDSs, initiating a rebuildprocess, or initiating at least one of a decommissioning of the SU, aquarantine of the SU, or a higher level of security regarding access tothe SU.
 3. The computing device of claim 1, wherein the processingcircuitry is further configured to execute the operational instructionsto: based on determination that the new integrity check value does notsubstantially matches the extracted integrity check value: initiaterebuilding of the EDS portion of the one of the ICVL EDSs to produce arebuilt EDS; generate an integrity check value for the rebuilt EDS;generate an updated ICVL including the integrity check value for therebuilt EDS and integrity check values of the EDSs of the other ICVLEDSs; append the updated ICVL to the rebuilt EDS to produce a rebuiltICVL EDS; and send the rebuilt ICVL EDS to one of the SUs of the set ofSUs for storage therein.
 4. The computing device of claim 1, wherein theprocessing circuitry is further configured to execute the operationalinstructions to: based on determination that the likely cause is notmissing a revision update: initiate rebuilding of the EDS portion of theone of the ICVL EDSs to produce a rebuilt EDS; generate an integritycheck value for the rebuilt EDS; generate an updated ICVL including theintegrity check value for the rebuilt EDS and integrity check values ofthe EDSs of the other ICVL EDSs; append the updated ICVL to the rebuiltEDS to produce a rebuilt ICVL EDS; and send the rebuilt ICVL EDS to oneof the SUs of the set of SUs for storage therein.
 5. The computingdevice of claim 1, wherein the processing circuitry is furtherconfigured to execute the operational instructions to: based ondetermination that the appended ICVL of one of the ICVL EDSs of the readthreshold number of ICVL EDSs substantially matches the appended ICVL ofother ICVL EDSs of the read threshold number of ICVL EDSs, process therequest.
 6. The computing device of claim 1, wherein the processingcircuitry is further configured to execute the operational instructionsto: generate a set of integrity check values for a set of EDSs, whereinthe data segment of the data object is dispersed storage error encodedto produce the set of EDSs; generate an ICVL from the set of integritycheck values; append the ICVL to each EDS of the set of EDSs to producethe set of ICVL EDSs; and send the set of ICVL EDSs to the set of SUs ofthe DSN for storage therein.
 7. The computing device of claim 1, whereinthe computing device is one of the SUs within the DSN, a wireless smartphone, a laptop, a tablet, a personal computer (PC), a workstation, or avideo game device.
 8. The computing device of claim 1, wherein the DSNincludes at least one of a wireless communication system, a wire linedcommunication system, a non-public intranet system, a public internetsystem, a local area network (LAN), or a wide area network (WAN).
 9. Acomputing device comprising: an interface configured to interface andcommunicate with a dispersed storage network (DSN); memory that storesoperational instructions; and processing circuitry operably coupled tothe interface and to the memory, wherein the processing circuitry isconfigured to execute the operational instructions to: retrieve a readthreshold number of integrity check value list (ICVL) encoded dataslices (EDSs) of a set of ICVL EDSs from at least some storage units(SUs) of a set of SUs based on a request; determine whether an appendedICVL of each ICVL EDS of the read threshold number of ICVL EDSssubstantially match; generate a set of integrity check values for a setof EDSs, wherein a data segment of a data object is dispersed storageerror encoded to produce the set of EDSs; generate an ICVL from the setof integrity check values; append the ICVL to each EDS of the set ofEDSs to produce the set of ICVL EDSs; send the set of ICVL EDSs to theset of SUs of the DSN for storage therein; based on determination thatthe appended ICVL of one of the ICVL EDSs of the read threshold numberof ICVL EDSs does not substantially match the appended ICVL of otherICVL EDSs of the read threshold number of ICVL EDSs: determine a likelycause for the appended ICVL of the one of the ICVL EDSs notsubstantially matching the appended ICVL of the other ICVL EDSs; andbased on determination that the likely cause is an inaccurate ICVLappended to the one of the ICVL EDSs: calculate a new integrity checkvalue for an EDS portion of the one of the ICVL EDSs; extract anintegrity check value from the appended ICVL of one of the other ICVLEDSs to produce an extracted integrity check value; compare the newintegrity check value with the extracted integrity check value; andbased on determination that the new integrity check value substantiallymatches the extracted integrity check value, utilize the EDS in decodingof the read threshold number of EDSs to recover the data segment of thedata object; and based on determination that the appended ICVL of one ofthe ICVL EDSs of the read threshold number of ICVL EDSs substantiallymatches the appended ICVL of other ICVL EDSs of the read thresholdnumber of ICVL EDSs, process the request.
 10. The computing device ofclaim 9, wherein the processing circuitry is further configured toexecute the operational instructions to: based on determination that thelikely cause is not the inaccurate ICVL appended to the one of the ICVLEDSs and also is not missing a revision update, take at least onecorrective measure for an unauthorized modification that includes atleast one of sending a delete message to a SU storing the one of theICVL EDSs, initiating a rebuild process, or initiating at least one of adecommissioning of the SU, a quarantine of the SU, or a higher level ofsecurity regarding access to the SU.
 11. The computing device of claim9, wherein the processing circuitry is further configured to execute theoperational instructions to: based on determination that the newintegrity check value does not substantially matches the extractedintegrity check value: initiate rebuilding of the EDS portion of the oneof the ICVL EDSs to produce a rebuilt EDS; generate an integrity checkvalue for the rebuilt EDS; generate an updated ICVL including theintegrity check value for the rebuilt EDS and integrity check values ofthe EDSs of the other ICVL EDSs; append the updated ICVL to the rebuiltEDS to produce a rebuilt ICVL EDS; and send the rebuilt ICVL EDS to oneof the SUs of the set of SUs for storage therein.
 12. The computingdevice of claim 9, wherein the processing circuitry is furtherconfigured to execute the operational instructions to: based ondetermination that the likely cause is not missing a revision update:initiate rebuilding of the EDS portion of the one of the ICVL EDSs toproduce a rebuilt EDS; generate an integrity check value for the rebuiltEDS; generate an updated ICVL including the integrity check value forthe rebuilt EDS and integrity check values of the EDSs of the other ICVLEDSs; append the updated ICVL to the rebuilt EDS to produce a rebuiltICVL EDS; and send the rebuilt ICVL EDS to one of the SUs of the set ofSUs for storage therein.
 13. The computing device of claim 9, whereinthe computing device is one of the SUs within the DSN, a wireless smartphone, a laptop, a tablet, a personal computer (PC), a workstation, or avideo game device.
 14. The computing device of claim 9, wherein the DSNincludes at least one of a wireless communication system, a wire linedcommunication system, a non-public intranet system, a public internetsystem, a local area network (LAN), or a wide area network (WAN).
 15. Amethod for execution by a computing device, the method comprising:retrieving, via an interface configured to interface and communicatewith a dispersed storage network (DSN), a read threshold number ofintegrity check value list (ICVL) encoded data slices (EDSs) of a set ofICVL EDSs from at least some storage units (SUs) of a set of SUs withinthe DSN based on a request; determining whether an appended ICVL of eachICVL EDS of the read threshold number of ICVL EDSs substantially match;based on determination that the appended ICVL of one of the ICVL EDSs ofthe read threshold number of ICVL EDSs does not substantially match theappended ICVL of other ICVL EDSs of the read threshold number of ICVLEDSs: determining a likely cause for the appended ICVL of the one of theICVL EDSs not substantially matching the appended ICVL of the other ICVLEDSs; and based on determination that the likely cause is an inaccurateICVL appended to the one of the ICVL EDSs: calculating a new integritycheck value for an EDS portion of the one of the ICVL EDSs; extractingan integrity check value from the appended ICVL of one of the other ICVLEDSs to produce an extracted integrity check value; comparing the newintegrity check value with the extracted integrity check value; andbased on determination that the new integrity check value substantiallymatches the extracted integrity check value, utilizing the EDS indecoding of the read threshold number of EDSs to recover a data segmentof a data object.
 16. The method of claim 15 further comprising: basedon determination that the likely cause is not the inaccurate ICVLappended to the one of the ICVL EDSs and also is not missing a revisionupdate, taking at least one corrective measure for an unauthorizedmodification that includes at least one of sending a delete message to aSU storing the one of the ICVL EDSs, initiating a rebuild process, orinitiating at least one of a decommissioning of the SU, a quarantine ofthe SU, or a higher level of security regarding access to the SU. 17.The method of claim 15 further comprising: based on determination thatthe new integrity check value does not substantially matches theextracted integrity check value: initiating rebuilding of the EDSportion of the one of the ICVL EDSs to produce a rebuilt EDS; generatingan integrity check value for the rebuilt EDS; generating an updated ICVLincluding the integrity check value for the rebuilt EDS and integritycheck values of the EDSs of the other ICVL EDSs; appending the updatedICVL to the rebuilt EDS to produce a rebuilt ICVL EDS; and sending therebuilt ICVL EDS to one of the SUs of the set of SUs for storagetherein.
 18. The method of claim 15 further comprising: based ondetermination that the likely cause is not missing a revision update:initiating rebuilding of the EDS portion of the one of the ICVL EDSs toproduce a rebuilt EDS; generating an integrity check value for therebuilt EDS; generating an updated ICVL including the integrity checkvalue for the rebuilt EDS and integrity check values of the EDSs of theother ICVL EDSs; appending the updated ICVL to the rebuilt EDS toproduce a rebuilt ICVL EDS; and sending the rebuilt ICVL EDS to one ofthe SUs of the set of SUs for storage therein.
 19. The method of claim15, wherein the computing device is one of the SUs within the DSN, awireless smart phone, a laptop, a tablet, a personal computer (PC), aworkstation, or a video game device.
 20. The method of claim 15, whereinthe DSN includes at least one of a wireless communication system, a wirelined communication system, a non-public intranet system, a publicinternet system, a local area network (LAN), or a wide area network(WAN).